A highly independent and controllable dual‐band bandpass filter based on source‐load coupling with stub‐block isolation structure

Abstract

The main problem of dual‐band bandpass filter (BPF) structures is to control each passband performance individually, separately, and independently. This Letter is proposed a dual‐band BPF based on a source‐load coupling structure with stub‐block isolation to overcome the problem. The lower band resonator structure is placed on the top side, while the upper band resonator is placed at the bottom side, with the source‐load (SL) coupling structure in the middle. An additional stub‐block isolation structure is added to the center of the SL coupling structure. As a result, we have successfully designed an independent dual‐band bandpass filter with highly controllable working frequency/frequency center (fc), bandwidth (BW), reflection coefficient (S11), and isolation (ISO) between the passbands. The proposed dual‐band BPF was fabricated on an RT/Duroid 5880 substrate. Furthermore, this dual‐band BPF achieved an insertion loss/fractional bandwidth of 0.48 dB/7.71% and 0.35 dB/12.37% at 1.82 and 2.58 GHz, respectively. The good agreement between the simulated and measured results validates the proposed method.